"Thousands of demonstrators massed on streets surrounding Istanbul's central Taksim Square, long a venue for political unrest, while protests erupted in the capital Ankara and the Aegean coastal city of Izmir."

NPR's Andy Carvin has been following developments he's monitoring on Twitter.

The protests were sparked Friday when police broke up a four-day sit-in by people angered about redevelopment plans for a portion of Taksim Square, known as Gezi Park. The Gezi Park protest started Monday after trees were removed as part of the redevelopment plan. The controversial redevelopment project is aimed at easing congestion around Taksim Square but also involves building a shopping center over Gezi Park.

But the protests quickly widened into a broader demonstration against Prime Minister Recep Tayyip Erdogan's administration, according to The Associated Press.

Al-Jazeera reports that the protests in Ankara saw police firing tear gas "to disperse people trying to reach the headquarters of the ruling Justice and Development Party (AKP).":

"The demonstrators, mostly young supporters of the opposition Republican People's Party, had planned to protest against new laws restricting the sale of alcohol and chanted: 'Everywhere is resistance, Everywhere is Taksim.' "

Mert Burge, 18, who came to support the protesters after reading on Twitter about the police use of tear gas, told the AP that "this isn't just about trees anymore, it's about all of the pressure we're under from this government."

"We're fed up, we don't like the direction the country is headed in," Burge said.